MARTINSBURG, W.Va. — The Bureau of Alcohol, Tobacco, Firearms and Explosives has been without a permanent director for six years, as President Obama recently noted. But even if someone were to be confirmed for the job, the agency’s ability to thwart gun violence is hamstrung by legislative restrictions and by loopholes in federal gun laws, many law enforcement officials and advocates of tighter gun regulations say.

For example, under current laws the bureau is prohibited from creating a federal registry of gun transactions. So while detectives on television tap a serial number into a computer and instantly identify the buyer of a firearm, the reality could not be more different.

When law enforcement officers recover a gun and serial number, workers at the bureau’s National Tracing Center here — a windowless warehouse-style building on a narrow road outside town — begin making their way through a series of phone calls, asking first the manufacturer, then the wholesaler and finally the dealer to search their files to identify the buyer of the firearm.

About a third of the time, the process involves digging through records sent in by companies that have closed, in many cases searching by hand through cardboard boxes filled with computer printouts, hand-scrawled index cards or even water-stained sheets of paper.

In an age when data is often available with a few keystrokes, the A.T.F. is forced to follow this manual routine because the idea of establishing a central database of gun transactions has been rejected by lawmakers in Congress, who have sided with the National Rifle Association, which argues that such a database poses a threat to the Second Amendment. In other countries, gun rights groups argue, governments have used gun registries to confiscate the firearms of law-abiding citizens.

Advocates for increased gun regulation, however, contend that in a country plagued by gun violence, a central registry could help keep firearms out of the hands of criminals and allow law enforcement officials to act more effectively to prevent gun crime.

As has been the case for decades, the A.T.F., the federal agency charged with enforcing gun laws and regulating the gun industry, is caught in the middle.

Law enforcement officials say that in theory, the A.T.F. could take a lead role in setting a national agenda for reducing gun crime, a goal that has gained renewed urgency with the school massacre in Newtown, Conn. But it is hampered, they say, by politically driven laws that make its job harder and by the ferocity of the debate over gun regulation.

“I think that they’ve really been muzzled over the last several years, at least, from doing their job effectively,” said Frederick H. Bealefeld III, a former police commissioner in Baltimore. “They’ve really kind of been the whipping agency, caught in the political turmoil of Washington on the gun issue.”

The bureau’s struggles are epitomized by its lack of a full-time director since Congress, prodded by the N.R.A., decided that the position should require Senate confirmation. That leadership vacuum, Mr. Bealefeld and others said, has inevitably depleted morale and kept the agency from developing a coherent agenda.

At a news conference last Wednesday, Mr. Obama called on the Senate to confirm a permanent director, saying lawmakers should “make this a priority early in the year.” But given the complicated politics, it may be difficult for the White House to get a director confirmed. Mr. Obama’s Republican predecessor, George W. Bush, was unable to do so.

In 2010, Mr. Obama nominated Andrew Traver, who is now the head of the bureau’s Denver division, for the post. But Mr. Traver, whose candidacy is opposed by the N.R.A., has yet to have a hearing, and his nomination has languished in the Senate Judiciary Committee. The senior Republican on the panel, Senator Charles E. Grassley of Iowa, has raised questions about Mr. Traver’s nomination, and his prospects for confirmation looked so dim that the White House told Democrats on the committee to make nominations for other posts a higher priority, according to a Senate Democratic aide.

The persistent controversy over the A.T.F.’s role, historians say, also contributed to its neglect in the financing bonanza that followed the Sept. 11 terrorist attacks. While other law enforcement agencies like the F.B.I. have benefited from greatly increased budgets and staffing, the A.T.F.’s budget has remained largely stagnant, increasing to about $1.1 billion in the 2012 fiscal year from just over $850 million a decade ago.

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Lawmakers in Congress have resisted efforts to establish a database for gun sales, and many records are still handwritten.Credit
Michael Stravato for The New York Times

The bureau’s tracing center performed 344,447 gun traces in the 2012 fiscal year, but its staffing is no higher than it was in 2004, according to its chief, Charles Houser. Still, he added, the center manages to complete urgent traces in about an hour, and routine traces are done within several days.

The distrust between the A.T.F. and gun rights groups is longstanding. The bitterness runs so deep that some critics of the agency are still angry about events from more than 40 years ago. Alan Gottlieb, the founder and executive vice president of the Second Amendment Foundation, cited a 1971 case in which A.T.F. agents raided the apartment of Ken Ballew in Silver Spring, Md., in the belief that he was stockpiling unregistered grenades. Agents found a cache of weapons, according to a lawsuit filed in the case, and Mr. Ballew was shot in the head after pointing a revolver in the agents’ direction.

The 1992 siege of Ruby Ridge in Idaho and the 1993 raid on the Branch Davidian complex near Waco, Tex., are also sore points, Mr. Gottlieb said.

“Waco is not something that made us feel warm and fuzzy about A.T.F.,” he said.

Mr. Gottlieb said the “low point” came with the bungled gun trafficking investigation known as Operation Fast and Furious, in which A.T.F. agents, in an effort to trace guns to a network based in Arizona, did not quickly intervene as the weapons were smuggled over the border to Mexico. Last Wednesday, in a development that may inflame the controversy further, Mr. Grassley sent letters to Attorney General Eric H. Holder Jr. and the Justice Department’s Office of the Inspector General demanding an investigation and requesting more information about why a gun bought by an A.T.F. agent involved in Operation Fast and Furious was found at the scene of a homicide in Mexico.

Marc Willis, a spokesman for the A.T.F., said the bureau could not comment on continuing investigations.

The bureau’s acting director, B. Todd Jones, who was installed in the summer of 2011 to revamp the agency after the trafficking investigation, has said he has increased oversight and has carried out changes recommended by the inspector general in a report in September.

Yet law enforcement officials and criminal justice experts who would like the A.T.F. to have greater latitude in fighting crime say its effectiveness in reducing gun violence is still hampered by a thicket of laws that limit the information it can obtain and constrain its day-to-day functioning.

The Firearm Owners Protection Act of 1986, for example, prohibits A.T.F. agents from making more than one unannounced inspection per year of licensed gun dealers. The law also reduced the falsification of records by dealers to a misdemeanor and put in place vague language defining what it meant to “engage in business” without a dealer’s license.

Both provisions, said William J. Vizzard, an emeritus professor of criminal justice at California State University, Sacramento, and a former A.T.F. special agent, made it more difficult for the bureau to go after gun sellers who broke the law.

The so-called Tiahrt amendments — named for Todd Tiahrt, a former Republican congressman from Kansas, and first attached as riders to appropriations bills in 2003 and 2004 — limited the A.T.F.’s ability to share tracing information on firearms linked to crimes with local and state law enforcement agencies and with the public. Those restrictions have been loosened in subsequent versions of the amendments. But under the most recent Tiahrt amendment, adopted in 2010, the A.T.F. still cannot release anything but aggregate data to the public. The amendment still prohibits the bureau from using tracing data in some legal proceedings to suspend or revoke a dealer’s license, and it requires that records of background checks of gun buyers be destroyed within 24 hours of approval. Advocates of tighter regulation say this makes it harder to identify dealers who falsify records or buyers who make “straw” purchases for others.

Mr. Gottlieb said the Tiahrt amendment protected data “from people who are anti-gun rights who want to manipulate things” to bolster support for gun regulation.

Congress has long resisted the idea of a central transaction database.

David Kopel, a lawyer and the Second Amendment project director at the Independence Institute, a research group concerned with individual choice, said Congress was aware that a registry could be misused. “We don’t have an automated database of everybody who’s had an abortion or of anyone who owns controversial books,” he said.

But Mr. Bealefeld, the former Baltimore commissioner, said the notion that a central database would create “some Orwellian Big Brother oversight that’s going to monitor target shooters and hunters and sneak into their houses in the dead of night to steal their rifles and their pistols” was “more fiction than reality.”

“I’ve hunted since I was 7 years old,” he said, “and I don’t live in fear that anyone’s going to come and take my hunting rifles.”

A version of this article appears in print on December 26, 2012, on page A1 of the New York edition with the headline: Legal Curbs Said To Hamper A.T.F. In Gun Inquiries. Order Reprints|Today's Paper|Subscribe